U.S. Pat. No. 3,994,222 discloses a printing unit having ink distributor rolls which rotate to distribute ink in the printing unit. The printing unit disclosed in the '222 patent also has a vibrator mechanism for vibrating the ink distributor rolls by moving them back and forth along their axes. The vibrating movements of the ink distributor rolls assist in evenly distributing the film of ink on the rolls. The vibrator mechanism includes a rotating shaft and a plurality of eccentrics which are mounted on the shaft to rotate with the shaft. The rotating eccentrics operate a lever mechanism which moves the ink distributor rolls back and forth along their axes. Axial movement of the ink distributor rolls is resisted by the inertia of the ink distributor rolls, and by the friction between the ink distributor rolls and the other rolls which they slide against when moving axially. Such resistance is transmitted by the rotating eccentrics to the rotating shaft in the form of torques which resist rotation of the shaft. Because the shaft is rotated by the same gear train that rotates the printing cylinders in the printing press, the torques applied to the shaft by the eccentrics can be transmitted through the gear train to the rotating printing cylinders. Such transmitted torques can mar the printed image.